This invention relates to photographic materials. In a preferred form it relates to a duplitized photographic reflection and transmission display material.
It is known in the art that photographic display materials are utilized for advertising as well as decorative displays of photographic images. Since these display materials are used in advertising, the image quality of the display material is critical in expressing the quality message of the product or service being advertised. Further, a photographic display image needs to be high impact, as it attempts to draw consumer attention to the display material and the desired message being conveyed. Typical applications for display material include product and service advertising in public places such as airports, buses and sports stadiums, movie posters and fine art photography. The desired attributes of a quality, high impact photographic display material are a slight blue density minimum, durability, sharpness and flatness. Cost is also important, as display materials tend to be expensive compared with alternative display material technology such as lithographic images on paper. For display materials, traditional color paper is undesirable as it suffers from a lack of durability for the handling, photo processing and display of large format images.
Prior art photographic display materials historically have been classified as either reflection or transmission. Reflection display material typically is highly pigmented image supports with a light sensitive silver halide coating applied. Reflection display materials are typically used in commercial applications where an image is used to convey an idea or message. An application example of a reflection display material is product advertisement in a public area. Prior art reflection display materials have been optimized to provide a pleasing image using reflective light. Transmission display materials are used in commercial imaging applications and are typically backlit with a light source. Transmission display materials are typically a clear support with a light sensitive silver halide and an incorporated diffuser (to hide the xe2x80x9cshow throughxe2x80x9d of the lamps used to provide viewing illumination) or a substantially transparent support coated with a light sensitive silver halide emulsion which requires a diffusing screen to be placed behind the material as a means to obscure the xe2x80x9cshow throughxe2x80x9d of the lamps used to provide illumination to the media. Prior art transmission display materials have been optimized to provide a pleasing image when the image is backlit with a variety of light sources. Because prior art reflection and transmission products have been optimized to be either a reflection display image or a transmission display image, two separate product designs must exist in manufacturing and two inventories of display materials must be maintained at the photo-finishing printing site. Further, when the quality of the backlighting for transmission display material is diminished when for example, a backlight bums out or the output of the backlight decreases with the age, the transmission image will appear dark and reduce the commercial value of the image. It would be desirable if an image support could function both as a reflection and transmission display material.
Prior art transmission display materials use a high coverage of light sensitive silver halide emulsion to increase the density of the image compared to photographic reflection print materials. While increasing the coverage does increase the density of the image in transmission space, the time to image development is also increased as the coverage increases. Typically, a high-density transmission display material has a developer time of at least 110 seconds compared to a developer time of 45 seconds or less for photographic print materials. Prior art high-density transmission display materials, when processed, reduce the productivity of the development lab. Further, coating a high coverage of emulsion requires additional drying of the emulsion in manufacturing, which reduces the productivity of emulsion coating machines. It would be desirable if a transmission display material was high in density and had a developer time less than 50 seconds.
Prior art reflection photographic materials with a polyester base use a TiO2 pigmented polyester base onto which light sensitive silver halide emulsions are coated. It has been proposed in WO 94/04961 to use opaque polyester containing 10% to 25% TiO2 for a photographic support. The TiO2 in the polyester gives the reflection display materials an undesirable opalescent appearance. The TiO2 pigmented polyester also is expensive because the TiO2 must be dispersed into the entire thickness, typically from 100 to 180 xcexcm. The TiO2 used in this fashion also gives the polyester support a slight yellow tint, which is undesirable for a photographic display material. For use as a photographic display material, the polyester support containing TiO2 must be tinted blue to offset the yellow coloration, and this, in turn, results in a loss in desirable whiteness and adding cost to the display material.
Prior art photographic display material uses polyester as a base for the support. Typically the polyester support is from 150 to 250 micrometers thick to provide the required stiffness. Prior art photographic display materials are typically coated with light sensitive silver halide imaging layers on one side of the support. Exposure devices have been built to expose only one side of prior art display materials thus there is little concern for print platen design. For example, exposure devices that use a vacuum roll for holding the media during exposing typically employ slots for vacuum. These slots act as xe2x80x9cblack trapsxe2x80x9d (areas were exposing energy will be lost and have little secondary reflection) that in a duplitized emulsion system can result in uneven density of the backside image.
In U.S. Pat. No. 6,030,756 duplitized silver halide imaging layers are discussed for use as a display material. In U.S. Pat. No. 6,030,756, both the top and bottom images are exposed by exposing the top side silver halide imaging layers. The display material in U.S. Pat. No. 6,030,756 is capable of giving a good image when viewed in either reflection or transmission mode; however, the display material in U.S. Pat. No. 6,030,756 suffers from uneven backside image density when placed against a non-uniform reflecting platen.
In simultaneously filed Docket 80,701, U.S. application Ser. No. 09/731,354, titled xe2x80x9cPOLYOLEFIN BASE DISPLAY MATERIAL WITH TONE ENHANCING LAYERxe2x80x9d is disclosed a method to improve the backside imaging efficiency by the addition of a tone enhancing layer in combination with an antihalation layer. This method employs a tone enhancing layer to avoid the problem of greatly diminished imaging efficiency of the backside emulsions that is associated with using an antihalation layer alone. Although the process produces pleasing product, it has been found that the maximum achievable density of the element when viewed in transmission mode is still lower than prior art transmission only display materials. This tends to make images look xe2x80x9cflatxe2x80x9d and desaturated in comparison to prior art transmission display materials. Further, use of high levels of reflective material in the tone enhancing layer can degrade the color reproduction of the transmission element because of an unwanted increase in blue Dmin. In order to compensate for the less than desired amount of transmission density, the amounts of silver, gel, and coupler can be increased on the backside of the element. However, as more of materials are used for the backside of the element, the total thickness of the coated element is increased, and the process sensitivity of the element is degraded.
There is a continuing need for an improved product that will present a bright reflective image when viewed directly and also provide a sharp bright image of sufficient dye density when backlit.
It is an object of the invention to overcome disadvantages of display materials.
It is another object to provide a superior, lower cost, and stronger display material.
It is another object to provide a backside image of sufficient dye density when the only exposing light is on the front side of the display element that is not compromised by uneven densities formed on the backside of the display element.
These and other objects of the invention are accomplished by a photographic element comprising a base material, at least one exposure side photosensitive silver halide layer, and at least one backside photosensitive silver halide layer, wherein said face side photosensitive layer has lower speed than said backside photosensitive layer, and wherein said base material has a percent transmission of between 35 and 60%.
The invention provides a material that will, when imaged and developed, result in a bright sharp reflective image when viewed in ambient front surface lighting conditions, as well as allowing for a pleasing image of sufficient dye density when illuminated with a transmission light source. In a preferred form the invention provides a product that has a silver halide image on each side but still retains a single exposure step and short processing time.